The present invention generally relates to medical sensors and more particularly pertains to sensors that generate data indicative of a patient's movements or activity.
Patients are routinely monitored with respect to certain parameters that may be affected by the patient's activity. The effect may be the result of a physiological change resulting from such activity, a variation in the sensor/patient interface or some alteration of the signal after its generation and during transmission to the related instrumentation. It may therefore be most beneficial to have a record of the patient's activity to assist in interpreting data collected with respect to the parameter of interest. "Motion artifacts" can thereby be quickly identified, as can the data that is generated during periods of activity and periods of inactivity.
In testing patients for sleep disordered breathing and other sleep disorders it is frequently desirable to determine whether the patient is actually asleep. An EEG signal would of course readily facilitate a sleep-awake determination but such equipment is not always available. Alternatively, it has been found that a motion-detecting device fastened about the wrist area is quite an effective substitute as activity of the hand/wrist/arm is a fairly reliable indication of being awake.
Motion transducers for monitoring patient activity typically employ piezo-film material which generates an electrical signal when mechanically disturbed. Such material has heretofore been incorporated in for example a bracelet from which electrical leads extend to instrumentation where the generated signals are processed and recorded or otherwise made available for analysis.
Disadvantages associated with previously used activity sensors are inherent in the resulting multiplicity of the various sensors and wires extending from the "instrumented" patient. The complexity of such an array not only complicates the tasks of medical personnel but also encumbers the patient. Furthermore, some patients fear the presence of and the attachment to the various devices. As a result, it would be most desirable to reduce the apparent complexity of monitoring systems without sacrificing the quality and quantity of information gathered thereby.